Pseudoknots are one of the major structural motifs which allow RNAs to fold into rather compact forms. Pseudoknots are also important signals governing the regulation of certain mRNAs. In Moloney Murine Leukemia virus, a pseudoknot is known to be important in regulating the degree of mRNA readthrough, hence establishing the amount of gag and gag-pol protein being made. The mechanism of the readthrough event is unknown. In general, there are only a few incomplete studies on the folding of pseudoknots, and this study aims to be a relatively complete thermodynamic description of the folding energetics of a pseudoknot. The calorimetry data is an essential complement to the UV hyperchromcity data already in hand. The combination of these two data sets will aid in determining the unfolding of this RNA. It is envisioned that such data will be useful in determining the mechansim of readthrough.